The Section 1983 provocation defense allows juries in certain cases to consider "provocative" actions of cops prior to using deadly force in assessing whether ultimate use of deadly force was justifiable.
The case of Sheehan v. City and County of San Francisco arose after a mentally ill woman was shot and nearly killed by police officers who entered her apartment once under justifiable circumstances and then again under constitutionally questionable circumstances. The Court held that if the jury decided the second entrance amounted to a unconstitutional search then it could consider that violation in assessing whether the subsequent use of deadly force was justified.
The Court held: "Under our case law...officers may be held liable for an otherwise lawful defensive use of deadly force when they intentionally or recklessly provoke a violent confrontation by actions that rise to the level of an independent Fourth Amendment violation."
The plaintiff presented testimony from a police practices expert who explained that when dealing with someone who is mentally ill, "officers are trained not to unreasonably agitate or excite the person, to contain the person, to respect the person's comfort zone, to use nonthreatening communications and to employ the passage of time to their advantage."
In Sheehan v. City and County of San Francisco, the Court also held that the Americans With Disabilities Act covers police encounters with people suffering from mental illness.
Another helpful case in the area of deadly force police shootings and mentally ill, agitated or despairing people was issued by the California Supreme Court in 2013. In that case, Hayes v. City of San Diego, the state's highest court held that in state tort cases juries can consider preshoot conduct in determining whether a cop's deadly force police shooting was negligent.